1. Field of the Invention
The present invention relates to a method and device for position detection, and more particularly, to a method and device for depressed position detection.
2. Description of the Prior Art
In U.S. Patent Application Publication No. 2007/0198926, Jouget et al. discloses a device for detecting position, which includes an upper electrode layer and a lower electrode layer. The upper and lower electrode layers include a plurality of conductive stripes arranged in parallel in different directions. The upper and lower electrode layers are separated from each other by insulating spacers interposed therebetween. The conductive stripes of the upper electrode layer are sequentially driven, and while each of the conductive stripes of the upper electrode layer is being driven, all conductive stripes in the lower electrode layer will be sequentially sensed once, thereby all intersecting points intersected by the stripes in the upper and lower electrode layers can be detected. In other words, when a stripe in the upper electrode layer being driven and a stripe in the lower electrode layer being sensed are depressed and made to contact each other, current flows from the driven stripe of the upper electrode layer to the sensed stripe of the lower electrode layer. By sensing signals in the stripes of the lower electrode layer, intersecting points that are depressed can be detected.
As shown in FIG. 1, when a finger depresses a surface, a plurality of intersecting points may be depressed simultaneously. During detection, signals in stripes of the lower electrode layer that are sensed later will be smaller. Thus, a different comparison value has to be used for different intersecting points in order to correctly determine depressions. However, this approach may still be not accurate enough when the number of depressed intersecting points is large. The establishment and storage for the comparison values for each intersecting point are clearly costly and not accurate enough. In addition, when higher resolution is demanded, the density of stripes needs to be increased, and in turn the sensing frequency needs to be lowered.
As can be seen, there are several shortcomings and inconvenience in the prior art requiring solutions that are not yet provided by any current methods and structures. Thus, a new technique is called for to address these long-standing problems.